by Marcus Chown
He moved the zinc balls along the wires by only a few millimetres at a time and worked like this all morning, steady, patient and unhurried. It was a joy to at last have his own laboratory, a luxury he had only dreamt of while at the University of Berlin, where until 1885 he had been the assistant of Hermann von Helmholtz, Germany’s most famous scientist. He was also perversely grateful for the economic recession which had recently engulfed the country; although it had left the department he headed bereft of students, the side effect was that he could devote himself to his research.
Hertz made yet another adjustment and stood stroking his neat beard while the thought went through his mind: was this really going to work? But a subtle change in the sound in the laboratory stopped him in mid-stroke. Frowning, he crouched next to his receiver.
There was a spark in the air gap! The gap was only a few hundredths of a millimetre wide and the spark was easier to hear than it was to see, but there was no doubt about it. It was definitely there.
He switched off the oscillator and the spark at the receiver died. He switched it on again and it reappeared. Something invisible was travelling through the air from his transmitter to his receiver! Although he could not prove it yet, he was sure he knew what it was. It had been predicted fifteen years earlier by a brilliant Scottish physicist who had died tragically young.
London, October 1862
When he left King’s College, James Clerk Maxwell felt like dancing on air. The autumn rain had stopped and the sun had come out, and he stopped opposite St Mary le Strand Church, utterly transfixed by the light sparkling on the surface of a puddle in the road. An hour ago, it had been only a suspicion in his mind. But now, having consulted a reference book in the library and plugged some numbers into his theory, it was a fact. He knew something that nobody in the history of the world had known before: he knew what light was.
The shout of a man on a hay wagon snapped him out of his reverie just in time to avoid his foot being crushed under a heavy cartwheel. He set off down the Strand, dodging the costermongers, flower sellers and vagrants. Although his usual habit was to walk the four miles from his home in Kensington to King’s each morning and catch the horse-drawn bus home, today, because of his desire to get to the library as quickly as possible, he had caught the bus in and was walking back.
He passed through Trafalgar Square, walked along Pall Mall East, turned up Haymarket and eventually came to the broad thoroughfare of Piccadilly. He had intended to go straight home – he had promised his wife, Katherine, they would go riding in Hyde Park – but as he came to Albemarle Street, he felt a compulsion to turn down it. Leaving the hubbub of the busy street behind him, he headed towards the building with a neo-classical façade and giant Corinthian pilasters at the end of the road.
The Royal Institution was where Michael Faraday had carried out his groundbreaking experiments on electricity and magnetism, and where the great man had instituted his Christmas Lectures for children and adults in 1825. Maxwell himself had also lectured there many times since his move to London from Aberdeen in 1860. During one triumphant lecture in May the previous year, he had even projected onto a big screen an image of a tartan ribbon – the world’s first colour ‘photograph’.2
Faraday was forty years Maxwell’s senior and an old man of seventy-one. Four years earlier, with his health failing, he had retired to Hampton Court, on the river to the west of London. He still made occasional visits to the Institution, and Maxwell had hoped that he might be fortunate enough to catch his friend there and share his discovery, but he was not in luck. With the permission of the Institution’s doorman, Maxwell went downstairs to the basement. In Faraday’s abandoned magnetic laboratory, he surveyed the coils and batteries and bottles of chemicals gathering dust. Without the experiments Faraday had carried out here, Maxwell knew that his remarkable discovery would have been impossible.
*
Faraday’s beginnings could not have been more different from Maxwell’s. Maxwell was heir to the 1,500-acre country estate of Glenlair in the Vale of Urr, near Dumfries in southern Scotland; it was from there that he had returned to London by train a day ago. Faraday, by contrast, was the son of a poor blacksmith.* At fourteen, he had been apprenticed to a bookbinder in Marylebone, just off Oxford Street, the route along which until only a few decades earlier condemned prisoners had been taken by cart from Newgate Prison to the gallows at Tyburn.
George Ribeau, a Huguenot refugee, had encouraged his apprentice to read the books that he was binding, many of which were scientific. In a bid to educate himself further, Faraday had attended weekly lectures at the City Philosophical Society, which were given by the society’s founder, the silversmith John Tatum, at his home in nearby Dorset Street. Inspired by the idea that he should believe only things he could demonstrate himself, Faraday started his own scientific experiments with what equipment he could afford on his meagre wages. He also made beautifully illustrated notes of Tatum’s lectures. These proved of crucial importance in getting him his life-changing break when Ribeau showed them to a client in his shop at 48 Blandford Street.
George Dance, an architect and artist, asked whether he could show Faraday’s notes to his father, a member of the Royal Institution. The next day, he returned to the shop with a ticket to a series of lectures by Humphry Davy. Like the golden ticket in Roald Dahl’s Charlie and the Chocolate Factory, the gift would turn out to be a passport to a better life for Faraday – though not immediately.
Davy was the most famous British scientist of his day, a man who had invented the miners’ safety lamp, discovered numerous new elements and who lectured with the showbiz razzmatazz of a music hall star.3 Half his audience were women, who reportedly swooned at his dashing presence. Faraday could barely contain his excitement when the evening of the first lecture came and he found himself among a chattering high-society crowd queuing beneath the flickering braziers of the Royal Institution.
In 1812, with his apprenticeship with Ribeau nearing its end, the twenty-one-year-old Faraday took up a professional post, resigned to a future of bookbinding drudgery. But he had a piece of good fortune when Davy was temporarily blinded by an explosion in his laboratory and Dance Senior suggested that Faraday might help him; for a few euphoric days, he became his hero’s assistant.
Afterwards, Faraday was afraid that he might never experience the scientific life again. However, he had an idea, and, using the skills he had acquired during his apprenticeship, he bound the notes he had taken during the Royal Institution lectures and sent them to Davy. It was a long shot, but on Christmas Eve he received a reply, promising him an interview in the New Year. The interview happened, but Faraday was plunged back into gloom when Davy said he had no vacancy.4 Then, one day, there was a miracle. A carriage drew up outside the Faradays’ house and a footman got down with a letter from Davy. He had fired his bottlewasher for fighting. The job, if he wanted it, was Faraday’s.
Davy was by this time the greatest scientist in Europe. His native country had knighted him, and France so revered him that it had awarded him the Napoleon Prize, even though it was at war with Britain. But Davy’s greatest success would turn out to be Michael Faraday.
Both Davy and Faraday, who eventually became his assistant, were fascinated by electricity. Davy had pioneered the field of ‘electrochemistry’, the technique by which he had isolated nine chemical elements, including potassium, sodium, calcium, barium, strontium and magnesium.
At the beginning of the nineteenth century, electricity was at the forefront of science and the popular imagination. It seemed so mysterious and unearthly that some even considered it satanic. Luigi Galvani’s discovery in around 1781 that electricity could twitch the leg of a dead frog had inspired the precocious eighteen-year-old Mary Shelley to write Frankenstein in 1818.5 But the most significant development of the time was Alessandro Volta’s invention of the battery in 1799; by generating a continuous current, it made possible the scientific study of electricity.6
However, it was the news of a sensational discovery in Denmark that caused Davy and Faraday to drop everything. On 21 April 1820, Hans Christian Ørsted was lecturing at the University of Copenhagen when he noticed that a compass needle was deflected from magnetic north whenever he switched the electric current in a nearby wire on or off. The needle was deflected exactly as it would have been had it been close to a magnet; the unavoidable conclusion was that a current-carrying wire was a magnet. Might this discovery even explain why some materials such as iron were magnetic? Might electric currents be circulating deep inside those materials? No one had guessed it before, but there was a connection between electricity and magnetism.
On 4 September 1821, Faraday used the effect discovered by Ørsted in an ingenious way.7 In his basement magnetic laboratory, he arranged a current-carrying wire so that it was continually deflected by a fixed magnet and so circled endlessly. It was not a very practical arrangement – it involved a bath of conducting mercury, which was highly toxic – but it proved the principle of the electric motor. Actually, Faraday had created the world’s first electric motor the day before, using a fixed wire and an endlessly circling magnet rather than a fixed magnet and an endlessly circling wire.
Maxwell would have loved to have witnessed that magnet circling under the influence of a mysterious but invisible force while horse-drawn carriages rumbled past on Albemarle Street. It must have seemed as if some impossible wonder from the distant future had fallen into nineteenth-century London through a crack in time. Faraday had been with his fourteen-year-old nephew George, and the pair of them had been so euphoric at the sight of the endlessly circling magnet that they had danced around the laboratory table, before heading off to a circus to celebrate.
The obvious question was: If electricity could create magnetism, could magnetism create electricity? It took Faraday until the summer of 1831 to find the answer, by which time Davy had died and he had succeeded him as Director of the Royal Institution.
Shortly after Ørsted’s discovery that a current-carrying wire behaves like a magnet, the French scientist André-Marie Ampère, ‘the Newton of Electricity’, had found it was possible to boost the effect by creating a cylindrical spiral out of wire.8 The more turns of wire in such a ‘solenoid’, the more powerful its magnetic effect. The proviso was that neighbouring sections of wire should not touch each other so that electricity leaked between them, which required interposing ‘insulating’ materials that did not conduct electricity.
Faraday turned to a solenoid in his attempt to use magnetism to create electricity. Iron was known to greatly enhance the magnetism of a solenoid, so he used it in the form of a ring that was fifteen centimetres in diameter. Around either side of the ring he wound a tight spiral of wire. Between each turn of the coil and its neighbour he interposed lengths of string, and he used sheets of cloth to insulate each layer from the next and from the iron ring. Although the two solenoids were physically unconnected, Faraday expected that when an electric current went through the first coil, turning it into a magnet, its magnetic tendrils would reach through the air to the second solenoid.
Faraday flipped a switch, sending an electric current through the first solenoid; to his delight, a current appeared fleetingly in the second coil. He then switched off the current in the first solenoid and a current appeared in the second coil – this time, bafflingly, flowing in the opposite direction. It was an epoch-making discovery: he had succeeded in making electricity from magnetism.
Faraday later found an easier way to achieve the same end, by simply inserting a bar magnet into the coil of a solenoid. When he pushed it in, a current flowed one way, and when he pulled it out, it flowed the other way. Faraday did not know it, but his discovery of ‘electromagnetic induction’ would change the world, leading to the development of ‘dynamos’ capable of the large-scale generation of electrical power.
That electricity and magnetism were connected was now beyond any doubt, but the fundamental questions remained. What was electricity? And what was magnetism? Although these mysteries continued to tantalise Faraday, his groundbreaking experiments had given him a feel for how electricity and magnetism worked, which led him to entertain a radical – in fact, heretical – idea.
When Faraday held a piece of iron close to a magnet, he could feel the magnetic force of attraction reaching out to grab it and concluded that there must be something invisible but real in the air in the space around it. And when he rubbed a piece of amber with fur, ‘charging’ it with ‘static’ electricity, it grabbed tiny scraps of paper, leading him to believe that there was something invisible but real in the air around the electric charge.
In Faraday’s mind, a magnet set up a magnetic force ‘field’ around it, and it was this that acted on a piece of metal. Similarly, an electrically charged body set up an electric force field in the space around it, and it was this that acted on the scraps of paper. Faraday imagined he could almost see the fields, like a wind or swirling fog, permeating empty space.
In perceiving the world in this way he was completely alone. At the time, everybody thought that electric currents were the important thing, but Faraday was sure that the fields were key. To his mind, a conductor was merely a guide for an electric field, which existed in the space around the wire and was the principal carrier of energy. An electric current was merely a secondary effect, a flow of electric ‘charge’ urged on by the electric field where it happened to intersect the conductor.
The field idea revealed the pleasing symmetry in the discoveries of Ørsted and Faraday. Ørsted’s discovery that a current-carrying wire was a magnet showed that a changing electric field creates a magnetic field, and Faraday’s discovery of electromagnetic induction showed that a changing magnetic field generates an electric field.
The reason Faraday’s idea of the field was shocking and heretical was because of the success of Isaac Newton. The greatest scientist in history had been spectacularly successful in explaining another fundamental force – the force of gravity – as acting instantaneously across space. According to Newton’s ‘universal theory of gravity’, the gravitational effect of the Sun acts directly on the Earth, and there is no medium through which the force is transmitted. This idea of ‘instantaneous action at a distance’ is, of course, ludicrous. Newton himself said as much; it was just a piece of pragmatism that enabled him to obtain a workable theory. Unfortunately, the physicists who came after him were so in thrall to his theory of gravity that they overlooked his reservations and became wedded to the idea of forces that acted instantaneously at a distance.
It did not matter in the slightest that Newton would have been open to Faraday’s ideas, because the rest of the scientific profession believed that he would not have been. Faraday was ridiculed, and his humiliation was all the greater because he was self-taught from a humble background and knew next to no mathematics, the lingua franca of university-educated physicists.
The irony is that it was Faraday’s lack of mathematical knowledge that freed him from the straitjacket of Newtonian – or, at least, supposed Newtonian – thinking and enabled him to ‘see’ the electric and magnetic fields that pervade space, and with the intuition he gained from this worldview to design experiments that no one else would have thought of.
Maxwell, pretty much alone among nineteenth-century mathematical physicists, recognised the importance of Faraday and his work. Like him, he had developed a fascination with the conundrum of electricity and magnetism that bordered on obsession. In February 1854, embarking on a research career after completing his graduate studies at Trinity College, Cambridge, the twenty-three-year-old Maxwell had written to the physicist William Thomson to ask his advice on what he should read in order to get his head around the bewildering array of electrical and magnetic phenomena.
Thomson, who would later become Lord Kelvin, was beginning his involvement in the ambitious scheme to lay a telegraph cable under the Atlantic between Britain and America – the Apollo Program of its day – but neve
rtheless found time to recommend Faraday’s Experimental Researches in Electricity. The three-volume treatise was a masterful summary of everything that was known about the subject, much of which had been discovered by Faraday himself. In poring over its clear-cut descriptions of electrical and magnetic phenomena, Maxwell felt he was seeing into the mind of the man who had made them. Faraday was an experimenter with a crystal-clear vision who accepted nothing until he could demonstrate it himself. Maxwell was so impressed that he decided not to read any work on electricity by those who approached the subject through an analysis of forces acting at a distance until he was utterly familiar with Faraday’s work.
Maxwell was particularly taken by Faraday’s idea of electric and magnetic fields. In one simple demonstration Faraday had sprinkled iron filings around a bar magnet, the pattern revealed suggesting to him that there were ‘lines’ of magnetic force in the air around the magnet. When he had publicised this idea, it had caused other scientists to fall off their chairs with laughter, but by repeating the simple experiment Maxwell could see the truth in what Faraday had claimed.
The challenge was clear to Maxwell: to find a way of expressing Faraday’s visual ideas in the language of mathematics. As a first step, he set out to concoct a ‘toy model’ that mimicked Faraday’s results and with which he could make sense of them. It was not an easy task. He began with the idea that the magnetic and electric fields behaved like a fluid, governed by the mathematical laws of fluid flow and with the speed and direction of the flow at any point representing the density and direction of the lines of force. In February 1857, with some trepidation, he sent Faraday a preliminary paper on his progress entitled ‘On Faraday’s Lines of Force’. Although he had a strong feeling that Faraday was a kindred soul, he could not be sure that the older man would feel the same way about him.
